Strategies in Light Report: LED Sector Looking for Alternative Solutions to Spur Adoption of General Lighting

Strategies
in Light Report:LED
Sector Looking for Alternative Solutions to Spur Adoption of General Lighting

By Paula
Doe, SEMI

With the HB-LED
sector counting on affordable general lighting to drive its future growth,
device makers look at the potential for alternative substrates, innovative
packaging and statistical process control.

General Lighting Increasingly
Becomes the Driver in a Flattening Market

The
packaged LED device market will see modest 1.8 percent CAGR over the next five
years, to rise from $13.7 billion to some $15 billion by 2017, according to Strategies
Unlimited. With demand for other
applications maturing, most of this growth will need to come from general
lighting. Use of LEDs for the still small market of general lighting roughly
doubled in 2012, to reach $3.1 billion, barely edging out displays to become
the largest application for the first time, noted Strategies Unlimited director of LED market research Ella Shum. Sales for almost all other applications,
however, are trending down, as both overcapacity and improving manufacturing
push down prices, and applications across the board from headlights to TVs used
significantly fewer, brighter devices.
Strategies Unlimited counts in its total all devices >30lm/W, and as
industry technology improves, that means that a large number of off-spec but
reasonable quality components go into things like Christmas lights and light tubes
and strips now get counted as part of the mid- and high-brightness LED lighting
market, explained Vrinda Bhandarkar, SU’s director of LED lighting research.

Lm/W & Klm/$

Efficacy

Though
the overall market may be flat, most of the leading suppliers are seeing
healthy growth. Shum noted that many of
the top 10 component suppliers saw double digit increases in sales, led by Toyoda
Gosei at 37 percent, thanks to post-tsunami demand for energy savings in Japan,
and Lumens at 32 percent, thanks to growth of its packaging for Samsung. Philips Lumileds and Samsung saw 21-22
percent growth, followed by Sharp, Seoul Semiconductor and Cree at 14-18
percent. Everlight and LG Innotek, however, saw 1 percent declines. Several of these big players were squeezed
for capacity, and expanded by acquisitions or partnerships, with Nichia allying
with Citizen, LG with Showa Denko, and Epistar acquiring Huga Optotech, while
the giant Chinese shipping company San-an bought a chip maker in Taiwan
and hired a crowd of engineers from others.

This
growth comes as prices have continued to plunge towards what’s needed to drive
mass adoption of general solid state lighting. Average price per light output
dropped another 45 percent in 2012, to $3.45/klm, according to Strategies
Unlimited. Some leaders have pushed device efficiencies up and manufacturing
costs down to do markedly better, with Nichia reporting $2/klm with its low-cost
plastic QFN package and Cree optimizing all parts of the device and packaging
to introduce a commercial 200lm/W device.

Equipment
spending will likely decline another ~10 percent this year, to some $1.7
billion, according to SEMI’s Opto/LED Fab Forecast. Equipment investment dropped ~30 percent last
year to $1.9 billion after the 2011 boom fueled by aggressive Chinese
government subsidies, reported SEMI
CMO Tom Morrow. But that excess capacity in China is starting
to get utilized. Chinese LED fab utilization has recovered from its 39 percent
low in 2011 back up to 61 percent as of 3Q12.

China
LED Fab Utilization

While
general lighting will drive much of future LED growth, Osram Opto Semiconductor LED VP and GM Wolfgang Lex pointed out that 50 percent of LEDs will still
continue to be sold into applications other than lighting and displays — and
it’s those other applications with high-value products with specific demands of
their own that are actually driving much of the technology development. “It’s
these niches that are paying for the R&D to develop the technology, not
solid state lighting,” he noted.

“The
winners will be those with the best lumens per wafer, the rights to the IP, and
the money to develop the technology,” said Cree
SVP Norbert Hiller, noting that
displays would consolidate around the few big players, but the less mature lighting
market still had room for new ideas from a lot of different companies, known
and unknown.

Bringing Down Costs:
A Look at GaN-on-GaN, GaN-on-Si, and 6-in. Sapphire Substrates

University of California Santa Barbara
professor Shuji Nakamura argued that
GaN-on-aN LEDs, currently being manufactured by Soraa, which he co-founded, could
possibly increase lumen output by as much as tenfold, while reducing the cost
per lumen, as the expensive GaN substrates remain a relatively small portion of
total cost. GaN substrates mean no lattice or thermal mismatch and drastically
fewer dislocations, for easy current spreading and little droop even at high current
density. “Ammonothermal technology [for
GaN growth] will decrease cost in the near future,” argued Nakamura. Soraa is
working on an ARPA-E project to grow GaN crystals with a steel reactor lined
with insulating ceramic for the high heat and high-pressure growth chamber, instead
of the usual costly and hard-to-scale-up nickel super alloys.

German
epi wafer supplier AZZURRO, meanwhile,
is supplying 150mm-200mm GaN on silicon wafer templates, with the buffer layers
grown, ready for LED makers to largely use their existing epi processes to grow
the active layers on top. The company
has announced that Epistar has successfully migrated its LED structures to the
150mm templates. AZZURRO co-founder and EVP of business development Alexander Loesing suggests that LED
makers now using 2-inch wafers could potentially move to larger substrates with
limited capital investment by using the templates, doing the epi in house with
existing tools, then using a CMOS foundry to do the rest of the
processing. “We don’t believe people
will add 200mm lines, but will use a foundry. We are working on deals with
foundries for the whole process,” he said. The company grows its buffer layers on thick
silicon wafers with its proprietary and patented strain management to control the
bow. After LED makers grow their LED structures on the templates, they remove
the silicon with standard low-cost removal processes, for wafers with the 50µm bow
required for silicon lines. Loesing reported 445.2nm emission with a standard
deviation (std) of 2.53nm across the wafer. The company is also marketing GaN-on-Si
epiwafers to power semiconductor makers.

China’s Lattice Power reported it is
currently running some 10,000-15,000 2-inch GaN-on-Si wafers per month, with typical
performance of 130-140lm/W for 45mil chips for some 50 customers to prove the
process. It’s developing a 6-inch wafer version, where uniformity remains a bit
less, with standard deviation of ~3nm instead of the 1nm on 2-inch, but CTO Hanmin Zhao estimates that the company
will get 6-inch uniformity to a similar 1nm std by 3Q this year. He figures the
cost per 1mm chip will be about 30 percent less on silicon than on than sapphire,
using a vertical chip design. The 2-inch
vertical silicon devices are getting about 5 percent higher light output and 5
percent lower yields (70-80 percent) than the lateral sapphire alternative, but
about the same as the vertical sapphire version.

But
the best bet for cost reduction may still be six-inch sapphires, especially now
that there is industry progress on standards for the wafers, cassettes,
loadports and software needed to adopt the existing silicon-centric production
equipment to efficient commercial volume production of the thicker and more
bowed sapphire wafers, noted SEMI’s Morrow.

“We
believe when the market improves many will go to 4-6 inch sapphire, as prices
of 6-inch wafers come down, and as 6-inch offers about 9X more efficient
processing with its 9X more chips per wafer, since cost drives everything,”
says Rubicon CEO Raja Parvez. “Besides scaling, it also
brings the ability to use excess semiconductor equipment for post epi processing
for better uniformity and yield.” He figures only about 15 percent of the
industry uses 6-inch so far, 30-40 percent 4-inch, and about 50 percent still
on 2-inch, and not much change occurred in the last very challenging 18 months,
as LED makers had plenty of capacity and no desire to invest in new equipment
in the downturn. But as the industry recovers demand for higher quality and
specifications will drive users to flatter, cleaner, thinner, and larger wafers,
he suggests, noting that older generation wafers will no longer be good enough
as the market gets more sophisticated. “Standards will develop,” he notes. “At the
end of the day, this will help to further decrease costs.”

While
sapphire wafer prices have fallen sharply recently, the technology developed
for the LED industry is now drawing considerable interest for durable, scratch-resistant
camera lens covers for cameras and smart phones, or even for smart phone cover
plates, which could compete with LEDs for sapphire supply and potentially boost
wafer prices.

Wafer
makers are also looking to add value, by offering patterned sapphire surfaces
(PSS) for light extraction, which has typically been done by LED makers in
house as part of their device design. Rubicon is developing PSS in house for
6-inch wafers.

Rethinking LED Packaging

Bridgelux has taken an
innovative approach of packaging its newest family (Vero™) of LEDs with a
standard- footprint, multilayer plastic substrate with connectors, for “plug and play” connectivity and easy
integration of more features for smart lighting in the future, argues Jim
Miller, chief Sales and Marketing officer . The line includes multiple color
quality options with overlapping performance capabilities to cover a wide range
of different applications in one form factor to simplify the supply chain.
The chip-on-board platform offers thermally isolated solder pads, or an onboard
connector port for snap-in solder-free connections, for easy installation and
field upgrades. The standardized packaging is manufactured at a semiconductor
OSAT with automated processes which Bridgelux believes provides competitive
advantage. The substrate and packaging technology have been designed so
smart lighting features like light or occupancy sensors or other chips can be
readily integrated on to the same product platform.

Improving Yields with
Statistical Process Control

Software
and metrology suppliers noted progress in improving LED yields by tracking
parameters in line, and automating the analysis of what needs fixing when. Suppliers
argued for the need to monitor real-time variables like temperature,
reflectance and curvature in the epi process, and patterns in electrical and
optical wafer maps, and for analysis of how these measures relate to final yield,
and for alarm points for when things are out of spec and need adjustment. “The LED sector’s pain point is that although
it can see defects on inspection at various process points, isolating defects
to point of origin and establishing root cause still remains a challenge,” says
Steven Chen, KLA-Tencor process control technologist. By correlating epi defects to yield, KLA
found that while total defect counts did not correlate with yield, higher
densities of critical defects of interest did have significant impact. “The
inspection equipment’s defect detection sensitivity and classification
capabilities need to be matched with yield management software that ties all
the data together,” he notes. He estimated that identifying the killer defects
and applying inline controls by linking inspection results with defect analysis
solutions could potentially save a user $1 million per year by catching
problems earlier.

Rudolph Technologies’ Matthew Chriss, LED process control
engineer, noted that if fabs connected MES systems to their many MOCVD chambers
they could stop going through log books looking for the commonalities among low
yielding chambers, and get automated readouts of excursions to locate the
tools, pockets, processes, or settings causing problems before things get too
far out of spec. “The automated systems
may reduce the operators needed for a small reduction in personnel costs, but I
believe the much bigger value is in the consistent process control,” says Chriss. Laytec’s
CTO Kolja Haberland also
reported yield improvements from its system to monitor real-time temperature,
reflectance and curvature in the MOCVD tool and report when a reading moves
enough out of spec to impact yield.

Also visit the SEMICON China 2013 (March
19-21) website (www.semiconchina.org) to learn more about
the LED Manufacturing Pavilion and the LED China 2013 Conference. For information on LED programs at SEMICON
West 2013 (July 9-11), visit www.semiconwest.org.